1. Field of the Invention
The present invention is directed to a floor panel which is filled with a fluid based cementitious material and an apparatus and process for making a floor panel which has a pan made of steel or other suitable material which is filled with the cementitious material. The apparatus and process utilize the principal of forced removal of excess water (i.e., de-watering) to adjust the volume of the cementitious material to exactly fill the pan.
2. Discussion of the Background
Access floor panels are typically on the order of 2 feet square and from 1 to 11/2 inches thick. In order to eliminate gaps and unevenness, the panels must be made to close tolerances. Access floor panels are currently manufactured utilizing a concrete-filled galvanized steel pan configuration. The most common practice is to fill the pan to excess, allowing the concrete to partially cure, and then surface grinding the panel to a finished dimension as shown in FIG. 1. This requires the use of a belt grinder 1 and a sanding belt 2 which contacts the steel edge of the pan 4 and grinds the concrete 6. Grinding the steel of the pan 4 is not desirable because the galvanizing is removed leaving the steel unprotected. Alternate manufacturing methods such as injecting the concrete into a closed capacity mold containing the pan, as shown in FIG. 2, have been of limited success, particularly since the concrete 6 does not easily flow through the small sections common in access floor panels.
An example of an apparatus and method for forming a composite structural panel is shown in U.S. Pat. No. 3,952,402 to Mengeringhausen. This discloses a process of compacting concrete in a closed cavity. A more advantageous method and apparatus for the production of composite structural panels is desired, however.
The process of de-watering concrete is known, as exemplified by the prior art device shown in FIG. 2. In this example, slabs 8 of concrete having a dimension of, for example, 2".times.20".times.30".times. are regularly manufactured by compressing concrete 6 in a mold 10 and forcing the excess water 12 out through a filter media 14, which is attached to a lower portion 16 of a perforated top press head plate 18, which is then pressed against the upper surface 20 of the concrete 6 in the mold 10. The result is the slab 8, which is sufficiently rigid to stand on end for curing. The performance requirements of most access floor installations may be met with a composite panel of light weight aggregate concrete and commercial quality steel. The required thickness of the panel would be just over an inch depending on whether any additional reinforcement is necessary. The pan, prior to being filled, is typically fairly formable and flexible.
The use of hydraulic concrete presses is also known, as exemplified by the Fielding and Platt, Ltd., brochure entitled "Fielding Hydraulic Concrete Presses". The process shown therein consists of filling a mold with a wet mix concrete and then applying pressure until excess water has been expelled and compaction is complete. A discussion is also set forth regarding concrete products in the article by Alan Lilley, entitled "Precast Concrete Paving Products", a brochure published by Fielding and Platt, Ltd.
The foregoing procedures are all characterized by certain drawbacks or deficiencies in the manufacturing process, which have not allowed panels of required tolerances to yet be available. The disadvantage of leakage of material from the panel when being processed and the need for protecting the edge of the panel from chipping during handling and use has resulted in Applicants' directed research to solve these problems.
The prior art has also been characterized by having uneven transition between edges of adjacent panels. These edges have been of low durability, and this has therefore led to the edges chipping when a load is rolled over the panels.
An apparatus and process has also been sought for the purpose of minimizing manufacturing tolerances in pressing operations so as to allow for a tight fit of the pan in the mold.
There has also been a desire to manufacture floor panels which have trim members which help to secure the concrete within the pan, which allows for post machining of the panel, if needed, and which provides an aesthetically pleasing edge portion, which also resists chipping either during or after installation of an access floor system.